1. Field of the Invention
The present invention pertains to rope ladders, and more particularly to rope ladders wherein a damaged platform or rung thereof can be replaced without disengaging other than the damaged platform or rung from the rope or the like suspending the platforms or rungs.
2. Description of the Contemporary and/or Prior Art
Collapsible ladders, and more particularly ladders which have the platforms or rungs thereof suspended by flexible stiles, such as ropes or the like, have been put to various uses including shipboard applications. In such applications, the ladders usually are subjected not only to heavy use but also to a rather hostile environment. Therefore, it is essential that these ladders not only be sturdy and durable but they also must be serviceable in the event of wear or damage.
Various flexible ladders have been proposed which provide different means for affixing a rope, cable, or the like to a ladder platform, sometimes called a rung, wherein the rope passes through a hole disposed in the platform. Ladders configured in this manner are shown, for example, in U.S. Pat. Nos. 800,934, 898,286, 899,552, 1,611,768, 3,077,241, 4,177,878, and 4,241,809, and in British Pat. Nos. 217,766, 496,194, and 935,645. A common disadvantage of these ladders is that in the event one of the platforms thereof, disposed between other platforms, becomes damaged, other platforms in addition to the damaged platform must be disassembled from the rope in order to replace the damaged platform. In the case of some designs, numerous platforms have to be disengaged so that the entire ladder can be restrung. At best, this is a time consuming chore and where the ropes are affixed using lashing such as that shown in British Pat. Nos. 217,766, 496,194 and 935,645, a major reworking of the ladder is required.
One design avoiding the problem of having to remove several platforms of a ladder to replace a damaged platform is shown in U.S. Pat. No. 641,741 and British Pat. No. 599,349. In these ladder configurations a pair of ropes clamped together at spaced apart locations are employed. The platform ends are disposed between the clamped ropes. Although this will permit replacement of a single platform, a great sacrifice is made in terms of platform stability.
To enhance stability and to still provide the feature of being able to replace a single ladder platform, various ladder configurations have been proposed which provide a notch or slot into which a rope or cable can be clamped. While such ladder configurations do permit the desired platform removability, the means heretofore proposed for clamping the ropes or cables within the notches are less than optimum by a virtue of placing undue strain upon the ropes or cables employed, by permitting slippage of the platforms along the longitudinal axes of the ropes or cables, or by providing platforms which are not particularly stable.
U.S. Pat. Nos. 2,638,260 and 3,415,341 teach ladders which have rope type stiles that are retained within a recess in the edge of a rung. The ropes are straight when the ladder is in use and the rungs are affixed thereto through crimping engagement of elements which are disposed around the ropes and are engaged by the rungs. A crimping connection with a straight rope as taught in these two patents inherently suffers from loosening since most forces on the rungs will tend to open the crimps therefore causing rung slippage along the ropes. If the crimps are tightened to try to preclude slippage, it is likely that the rope will be damaged from abrasion.
British Pat. No. 798,371 teaches the retention of a rope in the notched end of a ladder rung by a compression type clamp. Such a configuration suffers from the same problems of slippage and/or rope damage as noted in regard to the previously mentioned patents which employ crimping engagement. In an apparent attempt to minimize the slippage problem, this patent teaches the crossing of the ropes between rungs.
An alternate approach is shown in U.S. Pat. No. 1,349,125 wherein a rung which is divided in half is provided. The halves of the rung are clamped around the ropes employed and protrusions are provided adjacent to the ropes so that the rungs will be somewhat limited in slippage. Unfortunately, uneven weight distribution will cause stress upon the fasteners used to join the rungs together and rung slippage or shearing of the fastener is possible.
Other rope ladder configurations are shown in U.S. Pat. Nos. 2,079,034 and 2,373,346 as well as French Pat. No. 471,433 and Dutch Pat. No. 43,380.
The present invention overcomes the problems associated with the prior art by providing a rope clamp for ladder platforms which firmly precludes slippage and which is divided into two halves that engage adjacent ropes disposed in rope notches located in a platform, the halves of the clamp being secured together in a fashion to cause the ropes to be securely sandwiched between the clamp halves and the rope notches.